1. Field of the Invention
The invention relates generally to the field of photography, and specifically to an artificial illumination control system for a camera. More particularly, the invention relates to an artificial illumination control system for controlling the energization of a source of artificial illumination in a normal (or full) flash mode of operation, where ambient light levels are too low for a proper daylight exposure, and in a fill (or fill-in) flash mode of operation, where ambient light levels are relatively high but certain portions of the subject to be photographed have significantly less light falling on them than surrounding portions of the subject.
2. Description of the Prior Art
When taking a picture under conditions at which the levels of ambient light intensity are relatively high, such as in bright sun, but certain portions of the subject to be photographed have significantly less light falling on them than surrounding portions of the subject, resulting in the formation of dark shadows on the subject, it is desirable to provide additional scene illumination from a source of artificial illumination, such as an electronic flash device, sometimes referred to as a "strobe" unit. Situations where a source of artificial illumination are used in relatively high ambient light levels are commonly referred to as a "fill" or "fill-in" mode of flash operation.
Cameras were recently introduced several years ago, for example the KODAK MEDALIST VR 35 Camera, manufactured by Eastman Kodak Company, Rochester, N.Y., which include a manually operated fill-flash switch. The fill-flash switch must be manually closed to provide a fill flash mode of operation for a built-in electronic flash unit, and it must be held closed at the same time the shutter release button is depressed to initiate the photographic exposure interval. Conversely, in the normal flash mode of operation for use in dimly lighted surroundings, the electronic flash unit is automatically energized.
Other known cameras operate an electronic flash unit either in a normal flash mode or in a fill flash mode each time a picture is taken. Typically, in these cameras, the flash output is varied in accordance with the ambient light level.
Still other cameras inhibit, i.e. render inoperative, an electronic flash unit or shift the control mode of the camera from flash photography to daylight photography whenever the subject to be photographed is located beyond an adequately operable distance for the flash output. See U.S. Pat. No. 4,501,481 granted Feb. 26, 1985. The Cross-Referenced Application
The application cross-referenced above discloses a "smart" flash control system which operates selectively in one of three flash related modes based only upon ambient light levels. The control system operates in a fill flash mode whenever the ambient light level is equal to or greater than a predetermined high (bright) level, providing the same flash output in all cases of bright light. Conversely, the control system operates in a full flash mode whenever the ambient light level is less than or equal to a predetermined low (dim) value, and it provides the same flash output in this mode as in the fill flash mode. If, however, the ambient light level falls somewhere between the predetermined low level and the predetermined high level, the control system operates in a no flash (ambient) mode where no artificial illumination is provided.